1) Field of the Disclosure
The disclosure relates generally to composite structures, and more particularly, to methods and systems for reducing porosity in composite structures, such as composite parts for aircraft.
2) Description of Related Art
Composite materials, such as carbon fiber-reinforced polymer (CFRP) materials, are used in the manufacture of a wide variety of structures and component parts due to their high strength and rigidity, low weight, corrosion resistance, and other favorable properties. In particular, in the manufacture of aircraft, CFRP composite structures and component parts are used in increasing quantities to form the fuselage, wings, tail sections, skin panels, and other component parts of the aircraft.
During the manufacture of CFRP composite structures, unwanted voids, or empty areas, in the composite material may be created due to issues in a manufacturing process or engineering design. For example, before the cure cycle of a CFRP composite structure, such voids may be created by air entrapped during a layup operation. In addition, for example, during the cure cycle of the CFRP composite structure, such voids may be created by expansion of entrapped air and/or volatiles such as absorbed moisture and gaseous reaction products.
Porosity is a measure, e.g., a percentage, of the void content in a material and is a fraction of the volume of voids over the total volume. Void mitigation and low porosity levels or low void content, e.g., less than 2%-5%, are desirable to achieve good mechanical properties, such as shear strength, and to ensure the performance of the composite structures.
In addition, during the manufacture of large composite parts, such large composite parts may typically undergo many hours, e.g., 12-24 hours or more, of a pre-cure vacuum hold under vacuum pressure, in order to remove or substantially remove air that may be entrapped between the layers of composite material. Such pre-cure vacuum hold may add significant time to the overall manufacturing process, thus increasing the overall cost of manufacturing large composite parts.
Accordingly, there is a need in the art for an improved method and system for reducing porosity in composite structures that provide advantages over known methods and systems.